It is well known that introduction of a trifluoromethyl group into various organic compounds brings many efficiencies such as improvement in physiological activities of medical and agricultural chemicals and improvement in performance of functional materials. Therefore, reaction reagents for direct trifluoromethylation of an organic compound have been studied heretofore.
Although S-(trifluoromethyl)dibenzothiophenium trifluoromethanesulfonate described in Non-patent Documents 1 to 5 is capable of converting a carbon-hydrogen bond in various organic compounds to a carbon-trifluoromethyl bond, defects thereof are that production of S-(trifluoromethyl)dibenzothiophenium trifluoromethanesulfonate is extremely complicated and is rather expensive.
Although non-patent Documents 6 and 7 disclose trifluoromethylation using dichlorodifluoromethane, dibromodifluoromethane or bromochlorodifluoromethane, and cadmium, zinc or copper, application thereof is restricted to a substitution reaction of a halogen in an organic halide with a trifluoromethyl group.
Non-patent Document 8 describes that benzenes are converted to the corresponding trifluoromethylbenzenes with use of (trifluoromethyl)phenyliodonium trifluoromethanesulfonate obtained by oxidizing trifluoromethyl iodide with hydrogen peroxide in trifluoroacetic anhydride and then reacting the resultant with trifluoromethanesulfonic acid and benzene. However, production of (trifluoromethyl)phenyliodonium trifluoromethanesulfonate is complicated and is industrially hard to employ.
Non-patent Document 9 discloses trifluoromethylation of nucleobases and benzenes using trifluoroacetic acid and xenon difluoride. However, xenon difluoride is not suitable for use in an industrial scale because xenon, which is a starting material of xenon difluoride, is expensive and xenon difluoride is unstable to water.
Non-patent Document 10 discloses a method using copper powder and trifluoromethyl iodide, as a process for direct trifluoromethylation of an organic compound with trifluoromethyl halide. However, this process has problems that it uses hexamethylphosphoric triamide, which is industrially hard to handle, as a solvent and that it uses a copper compound which imposes a heavy burden on the environment. Although another known method is that using trifluoromethyl iodide and triethylborane (Non-patent Document 11), an applicable substrate is restricted to a carbonyl compound which can undergo enolization with lithium diisopropyl amide. Moreover, Non-patent Document 12 discloses that benzenes, pyridines and pyrroles can be trifluoromethylated by the use of trifluoromethyl bromide, zinc and sulfur dioxide. This document also describes that the same reaction proceeds by the use of trifluoromethyl bromide and sodium dithionite. Because both methods use the toxic substance containing sulfur, they are industrially hard to use.
Patent Document 1 discloses perfluoroalkylation of benzenes using perfluoroalkyl iodide and di-tert-butyl peroxide. Di-tert-butyl peroxide used in this method is highly explosive and industrially hard to employ.
Non-patent Document 13 discloses a method of converting a carboxyl group on a furan ring to a trifluoromethyl group with sulfur tetrafluoride. However, the method has problems that an applicable substrate is restricted to that having a carboxyl group, and that toxic sulfur tetrafluoride is used.
On the other hand, although perfluorobutylation of benzenes with perfluorobutyl iodide in dimethyl sulfoxide in the presence of iron(II) sulfate and hydrogen peroxide (Non-patent Document 14) and perfluoropropylation and perfluorobutylation of pyrroles and indoles with perfluoropropyl iodide or perfluorobutyl iodide in dimethyl sulfoxide in the presence of iron(II) sulfate and hydrogen peroxide (Non-patent Document 15) are known, there is no reaction example using trifluoromethyl iodide and no description on a reaction reagent for trifluoromethylation according to the present invention.
Non-patent Document 1: Tetrahedron Letters, Vol. 31, pp. 3579-3582, 1990
Non-patent Document 2: Journal of the American Chemical Society, Vol. 115, pp. 2156-2164, 1993
Non-patent Document 3: Journal of Organic Chemistry, Vol. 59, pp. 5692-5699, 1994
Non-patent Document 4: Journal of Fluorine Chemistry, Vol. 74, pp. 77-82, 1995
Non-patent Document 5: Journal of Organic Chemistry, Vol. 68, pp. 8726-8729, 2003
Non-patent Document 6: Journal of the American Chemical Society, Vol. 107, pp. 5014-5015, 1985
Non-patent Document 7: Journal of the American Chemical Society, Vol. 108, pp. 832-834, 1986
Non-patent Document 8: Journal of Synthetic Organic Chemistry, Japan, Vol. 41, pp. 251-265, 1983
Non-patent Document 9: Journal of Organic Chemistry, Vol. 53, pp. 4582-4585, 1988
Non-patent Document 10: Journal of Chemical Society, Perkin Transaction I, pp. 2755-2761, 1980
Non-patent Document 11: Organic Letters, Vol. 7, pp. 4883-4885, 2005
Non-patent Document 12: Journal of Chemical Society, Perkin Transaction I, pp. 2293-2299, 1990
Non-patent Document 13: Journal of Fluorine Chemistry, Vol. 75, pp. 115-116, 1995
Patent Document 1: U.S. Pat. No. 3,271,441
Non-patent Document 14: Journal of Organic Chemistry, Vol. 62, pp. 7128-7136, 1997
Non-patent Document 15: Tetrahedron Letters, Vol. 34, pp. 3799-3800, 1993